A phase interpolator circuit can be used to provide a set of clock signals. The clock signals each include a phase that may be offset with respect to the other clock signals. The plurality of phase offset clock signals are useful to provide one or more clock signals having a clock edge in a desired relationship to another signal, typically a data signal. For example, in some applications data is sent between two integrated circuits that don't share a common clock. A phase interpolator circuit can be used to provide multiple clocks on a receiving integrated circuit, one of which is selected as an internal clock for data sampling. In another example, the clock signals may be automatically successively switched onto another circuit, i.e., to sweep the clock phases. This can provide timing measurements with increased resolution that are useful for high speed circuit testing. In many cases, it is desired that the clock phase sweeping operation be substantially error-free.